The present invention relates to article transfer systems; and more particularly to a robot hand for pickinq up irregularly shaped objects having a planar surface, such as composite plies.
In manufacturing and construction it is often necessary to grasp sheet materials of wood, glass, plastic, ceramic, metal or composite materials. Handling and positioning of such sheet materials frequently requires a large expenditure of manual labor. To reduce the large expense associated with such material handling, a number of systems have been designed to facilitate handling and positioning sheet materials.
One such device is the Sheet Orienting and Transporting Frame disclosed in the U.S. Pat. No. 4,228,993 to Cathers. This patent discloses a device in which sheets are grasped by suction cups mounted on the ends of engaging arms that extend from a base plate which is fixed on a movable support arm. The spacing of the suction cups may be periodically adjusted, so as to correspond to the shape of the sheets being grasped, by manually telescoping the engaging arms in and out and by manually adjusting the pivotal position of the arms about the point at which the arms are connected to the base plate. This transporting frame is best utilized for transporting sheets of substantially the same shape and size, or for transporting sheets in which the shape and size of the sheets being grasped changes only occasionally so that manual readjustment of the adjusting arms is only occasionally required. However, where sheets of a variety of shapes and sizes are to be transported or oriented and where the shape and size of the sheets being transported changes often, it becomes necessary to have a capability for rapidly readjusting the spacing of the suction cups over a large variety of configurations at just a moments notice. It is further necessary that such readjustment be achievable without time consuming manual readjustments of cup positions.
One vacuum grasping hand that is capable of grasping sheets of a variety of shapes and sizes includes a planar surface to which an array of vacuum cups are fixed so as to cover the surface. The vacuum cups are connected to a source of vacuum in a manner that permits the cups to be selectively connected to the vacuum source so that the spacing of the vacuum cups to which suction is being applied may be easily changed. When the shape of the surface being grasped changes, the cups to which the suction source is applied is correspondingly changed. A hand of this type has increased versatility, but the large array of vacuum cups and means for connecting the vacuum cups to the source of suction results in a heavy grasping hand that can only be held and manipulated with a large expenditure of energy by a large robot.
In another suction grasping hand, a grasping hand has been achieved which permits variable spacing of vacuum cups in a hand that weighs considerably less than the Northrup hand. The Vertol hand includes four cups mounted on opposite ends of two transverse members, each of which are connected to a rack which interacts with a rotating pinion. Rotating the pinion in the clockwise direction moves the cups further apart while rotating the pinion in the opposite direction brings the vacuum cups closer together. The hand permits a certain level of mechanical cup adjustment in a hand that is relatively light so as to be supportable and movable with a smaller expenditure of energy by a smaller robot than would be required with other larger hands. However, for grasping irregularly shaped sheets, it is desirable that each of the vacuum cups be movable with respect to each other and be capable of assuming irregular spacing. Such irregular spacing cannot be attained when vacuum cups are fixed on transverse members that are movable in only two directions.